It is the hope that a nuclear generator of electrical energy will operate without interruption; however, this goal has not yet been realized. The reactor installation must be periodically shut down in order to perform maintenance, replacements, and repairs. One of the subsystems of the nuclear installation is the conduit connection between the reactor vessel and the steam generator. The fluid level of the reactor vessel is cycled up and down to service the core of the reactor. At the same time, the steam generator must be decontaminated of radioactive material.
To decontaminate the steam generator, a temporary plug or dam is required in the outlet conduit from the steam generator connected to the reactor vessel. It is to be assumed that personnel may enter the generator water (or plenum) chamber through a manway which is usually about 16" in diameter. From this chamber the outlet conduit has an opening of about 30" in diameter and about a foot of the length of the internal wall of the conduit tapers in the direction of the reactor vessel. None of the plug structures in the present art have been satisfactory to isolate the reactor from the steam generator for decontamination purposes. More specifically, the prior art devices do not provide the flexibility required to seal between the dam structure and the irregularity of the internal wall of the conduit.